Voice operated control arrangement for radio telephone systems



May 16, 1933. E, R. TAYLOR ET Ar. 1,909,433

VOICE OPERATED CONTROL ARRANGEMENT FOR RADIO TELEPHONE SYSTEMS Filed Sept. lO, 1929 2 Sheets-Sheet l L EN SSN INVENTORS ATTORNEY May 16, 1933; E. R. TAYLOR ET AL VOICE OPERAvlED CONTROL ARRANGEMENT FOR RADIO TELEPHONE SYSTEMS Filed Sept. l0, 1929 2 Sheets-Sheet 2 INVENTORS w wlsnhyz:

ATTORNEY SEN E12@ BY Patented May 16, 1933 TATES EDMUND BJ. TAYLOR, OF NEW YORK, N. Y., ND SUIvINER B. WRIGHT, OF SOUTH GRANGE,

- NEVI JERSEY, .ASSIGNORS TO AMERICAN' TELEPHONE AND TELEGRAPH COMPANY A. CORPORATION OF NBV! YORK VOICE OPERATED CONTROL ARRANGEMENT FOR RADIO TELEPHONE`SYSTEMS Application filed. September 10, 1929. Serial No. 391,530.

In radio telephone systems, such, for eX-4 ample, as the radio telephone system between New York and Lon-don, a control station is provided at the terminals (New York and London) whereby technical operators and other supervisory attendants may readily ccntrol and adjust thevarious pieces or ap- I paratus located at the terminals and whereby suitable transmission 'adjustments may be made Jfor telephone transmission in either direction. At each terminal the control station is connected to the associated radio transmitter and radio receiver by a four-wire circuit comprising a transmission line eX- tending from the control station to the radio transmitting station for transmission in one direction and a separate line from the corresponding receiving station to the control .station for transmissionr in the opposite direction.

In existing arrangements of this type the suppression of singing and echo currents either over the local tour-wire circuit at each terminal or over the over-all four-wire circuit from terminal to terminal has been accomplished by providing duplicate voiceoperated apparatus at each terminal control station7 the apparatus at each terminal comprising a voice-operated device associated withfthe transmitting line to clear the transnitting line which is normally disabled and to disable the local receiving line and a second voice-operated device associated with the local receiving line to disable the local transmitting line. The transmission of noise from the local transmitting line through the radio transmitter at the end thereof to the associated radio receiver and thence into the receiving line during times that the receiving line was being used for reception, has heretofore been prevented by wide geographical separation and by use of directive radio methods. Likewise when the transmitting line and radio transmitter were employed for transmission undue interference from the radio transmitter into the local receiving line was kept at a minimum by having the radio transmitter and radio receiver associated with a given terminal widely separated lgeographicallyand by the-use of directive radio methods. Y Y

rlhere arecertain disadvantages in providing a wide geographical separation between the radiov transmitter and the radio receiver associated with the same terminal, and moreover, as the number of radio communication channels between the same terminals increases, it becomes increasingly difficult to locate an associated radio transmitter and radio receiver sutliciently :tar apart from each other to accomplish the desired end and at the same time prevent interference with similar radio stations. It is therefore desirable to locate the radio transmitter and the radio receiver associated with a given terminal in the same general neighborhood. For eXample, instead orn having the radio transmitter for the New York terminal at some point on Long Island the corresponding radio receiver in Maine, as is the case with the existing long wave transatlantic radio telephone system, there are many factors making it desirable to arrange both the radio transmitter and the radio receiver in Maine, with the receiving line of the connecting four-wire circuit running trom the receiving station to New York through or in the neighborhood of the radio transmitter. A similar geographical arrangement could o course be made for the London terminal. Y

Such an arrangement of the radio apparatus makes it necessary to provide special arrangements ior preventing the transmission of noise from the radio transmitter to the ra dio receiver and. thence over the receiving line during idle periods of the transmitting line. Due to the proximity of the radio transmitter to the radio receiver the transmission received from the local radio transmitter during transmission lover the transmitting linewill be sopmuch greater in volume than that received from the distant terminal that such interfering transmission may overload the receiving line and result in crosstalk in adjacent circuits or in distortion in normally received signals due to potentials set up by the overloading currents. rlhis makes it necessary to provide special arrangements for disabling the receiving circuit when the radio transmitter is transmitting.

Noise from the transmitter is prevented by maintaining the radio transmitter normally disabled and by providing an auxiliary voiceoperated arrangement for removing the disabling means whenever the transmitting line is used for transmission. The overloading of that portion of the receiving line extending from the radio transmitter staiton to the control station may be prevented by utilizing the same voice-operated apparatus at the radio transmitter for disabling the receiving line at the radio transmitter station. Where overloading occurs in that portion of the receiving line intervening between the radio transmitter and the radio receiver, such overloading may be prevented by providing auxiliary voice-operated equipment at the radio receiving station for disabling the radio receiving circuit at the radio receiver station when the associated radio transmitter is transmitting. Such voice-operated equipment may be made marginal, so that it will respond only to transmission from the local radio transmitter and not to transmission from the transmitter associated with the distant terminal, thus taking advantage of the fact that the transmission tromthe local transmitter is much greater in volume than that from the distant transmitter. lf desired the voice-operated apparatus at the radio receiving station may be controlled by a separate radio receiver provided with directive equipment so as to render it still further responsive to signals from the direction of the local radio transmitter and less responsive to signals from the direction of the distant transmitter.

it is desirable that the attendants at the control station should have supervision and control so far as possible over all the voiceoperated equipment associated with the circuit. Since, iler the rea-sens above given, it is `desirable to have auxiliary voice-operated equipment at the radio transmitter and radio receiver, and since such auxiliary equipment is not under the direct supervision and control ot' attendants at the control station, it is desirable that such auxiliary equipment be made as sensitive as possible so that it will respond to the initial parts of the telephone wave beore it reaches its peal value. lf the equipment is highly sensitive it will be possible to make the associated delay circuit smaller or even omit it Without causing clipping.

On the other hand the auxiliary voice operated equipment must not be operated by noise currents, and it it is made sensitive its operating circuit must be fairly free from noise. lf the four-wire circuit from the terminal to the radio equipment is so constructed as to be a high grade circuit and relatively free from noise as, for example, by laying it in cable, noise which might cause false operation or"v the voice-operated equipment at the radio station will be contined to that arising in connecting circuits which lead from the subscriber to the terminal control station. It such noise is prevented from getting to the radio transmitting station (and from thence to the local receiving station) the voice-operated equipment at the radio transmitting station and radio receiving station may be made very sensitive so that it will always respond to voice transmission. To prevent the terminal noise from being transmitted to the radio transmitter, it is necessary to provide equipment at the control station similar to that heretofore used in radio telephone circuit for suppressing echo and singing currents. Such apparatus will be so arranged as to maintain the transmitting line normally disabled except when transmission is taking place. The voice-op erated equipment associated with the transmitting line at the control station will be arranged to remove the disabling means therefrom and will also disable the receiving line when the transmitting line is used for transmission. y rllhis equipment may be adjusted as to its sensitivity by the control station attendant who may also by suitable adjustments control the volume of voice transmission to be applied to the circuit. The voice-operated equipment associated with the receiving line of the control station will be arranged to disable the transmitting line when signals are being received from the distant terminal. The voice-controlled apparatus at the terminal station may also be arranged for the switching operations incidental to the use of privacy mechanism where such mechanism is employed.

In the arrangement so far outlined, bearn ing in mind that similar apparatus is associated with both terminals, it will be evident that full echo suppressor equipment for twoway control is provided at both terminals;l

and if no further arrangements are provided than those above described, the time during which lock-out may take place by reason of the two subscribers talking at substantially the same time (thereby each seizing control ol` his own transmitting line while vthe four-wire circuits are loaded circuits.

lll?

'its function when the-alternating the receiving line is used for reception. Full;

echo-suppressor equipment is thus provided at the transmitting station. At the same time the voice-operated equipment at the control station is modified by connecting the receivvoice-operated device to the receiving line at a point nearer the radio receiver than the point which the disabling means is applied to the receiving line by the voiceoperatc-d device associated with the transmitting` line at the control. station. By this rearrangement of apparatus it will be evident j that il' the voice transmission from the distant terminal arrives at a point in the receiving line adJacent the local radio transmitter the voice-operated equipment associated 'th the transinitting` line at the radio i; a isinitter will be disabled and the distant r will then have control of the circuit.

This will be true even though the local talker has n-lready operated the voice-operated em ment associated with his transmitting line at the control station because the transmission arri ig over the receiving line from the distant talker can always operate the voice equipment associated with the receiving line at the control station to disable the transmitting line and the voice apparatus associated therewith at the control station.

A further feature of the invention involves the transmission oi alternating currents over the transmitting side of the four-wire circuit during the time that the circuit is norniallv `idle in order to enable an attendant at the radio transmitter station to make observations of the transmission equivalent of the circuit and to maire such minor adjustments of the transmission equivalent as may be necessary from time to time. llllhere such alternating currents are provided they may be used to control voice-operated equipment at the radio transmitter in such a manner that intead of performing its -liunctions when perform currents a'roresaid cease, these alternating currents being automatically interrupted whenever voice transmission takes place.

The invention will now be more fully understood from the following description voice currents are received, it will when read in connection with the accoinpanying drawings, Figs. l and 2 of which when ry voiceplace-d end to end disclose a preferred circuit arrangement embodying the invention.

Referring to the drawings, a terminal control station is illustrated which is connected' by means of a four-wire circuit to a radior transmitter and a radio receiver, it being understood that a similar arrangement is provided for the distant terminal. At the control station the four-wire circuit is associated by means of the usual hybrid coil lO witha terminal line L which may beV a toll circuit over which a subscriber may be connected to the system. Terminal line L is balanced by a suitable network `\l and is conpleted overcircuits RLl, RL1 and RLl at the control station.

il voice-operated apparatus is associated with the transmitting path at the control station and comprises an amplifier-detector TAD bridged across the circuit TLl and controlling a master relay TMl, which in turn 'controls switching relays 'lSSl and TSS1 whose contacts normally disable the transmitting path, and echo hangover relays TEE@l and TEHO, whose contacts when open disable the receiving path. A voice hangover relay TVI-lOl is also provided and is controlled by the master relay TMl which also controls the switching relays and echo hangover relays just described to give them a desired hangover. rlhe TSS relays are quickto operate and quick to release their armatures. r)She TEHO relays while quick to operate are slow to release their armatures.

All four relays are initially operated from the Contact oit the master relay TM'l, but as their release is determined by the voice hangover relay TVI-101 the armatures of the TSS r-elays will be held up after the master relay Tlwll has released during the hangover time of the relay TVHOl. The TEHG relays are also given an additional hangover time due to the fact that they are slow to release.

It desired a privacy mechanism PM of known type may be employed for rendering the voice currents unintelligible as they are transmitted over the line TLQ, the same mechanism functioning to restore to normal similarly distorted currents received from the ifm,

distant station. As this privacy mechanism PM is common to both the transmitting and receiving path, the TSS relays and the TEHO relays perform the additional Jfuncvon..

tion of controlling the association ot the privacy mechanism with the transmitting path or the receiving path exclusively. For example, When the TSS relays are in their normal released condition the transmitting paths TLl and 'iL/1 on either side ot the privacy mechanism are short-circuited so thac transmission cannot take place over tno transmittiua` path and through the privacy mechanism Pls/l. rllhe 'illliltl relays, which are also normally released, under the same conditions maintain their contacts closed. rl`hese contacts control balanced transiiormer arrangements, one in the receiving path lll/1 on one side of the privacy mechanism and the other in the path lili/1 on the other side thereof. These balanced transformer arrangements are so arranged that When the contacts or" th 'llllljftl relays are closed transmission through them will take place. llhen, however, the contacts are open, as is the case when transmission takes place over the transmitting line7 the balanced 'windings ot each transformer arrangement are connected in opposing relation so that transmission is prevented. Under these conditions transmission cannot taire place from the line HL2 through the circuit lll/1 to the privacy mechanism, anc transmission is also prevented from the privacy mechan'sm and over circuit ll/l to the circuit lLl. During the transmitting condition the short circuits across the path Till and across the line TLZ Will be opened by the TSS relays, so that transmission can take place from the circuit rlllil through the privacy mechanism to the transmitting line TLT A voice-operated apparatus is also associated with the receiving side orn the fourivire circuit, said apparatus comprisng an amplifier-detector Brill which controls a master relay lh/l1 which.l in turn, controls an echo hangover relay BEHI, lvl-Zhen the amplilier-detector respon ds to received trans mission, the later relay opens a circuit of the master relay 'lll/l1 associated with the transmitting side olf the circuit and tlc-roby prevents the operation ot the TSS relavs 'the TEE() relays so that the transmit ing path will be disabled While transmisison can taire place itreely over the receiving` path. The amplifier-detector Rill), may be bridged across either the recei path llln by me ot the Xl Wiring or it may be bridged across the receivin -nd orn the line lig by means oi the Yl Wiring. lflhen the former Wi `j is employed the arrangemezt so in r describen is that heretofore used in connection ivitl the transatlantic radio telephone system.

'lllil to delav the voice curave h d me to Aincense is provided for enabling' the relay REI-lOl to respond to the ampliiier-detector RADl to disable the master relay Tl l before the voice currents incoming from the receiving path can pass throufh the hybrid coil l0 and cause false operation of the amplifier-detector Tllll. A volume control device 'lVCl which may comprise an amplifier with an adjustable potentiometer is associated With the transmitting path rllil to enable an attendant to maintain the volume level substantially constant, a volume indicator TVL being provi led to enable the attendant to observe va riations in the volume as the speaker raises or lowers his voice. Amplifiers TA1 and TAl arc connected in the transmitting circuits Tl'il and Tijl, respectively, and simiiy, receiving ampliiiers ltlil and BA1 are connected in the receiving paths Rijl and lill, respectively. rlhe receiving path may also include a volume cont-rol apparatus RV@ and volume indicator HVL tor enabling the control station attendant to regulate the received volume.

assuming that the l Wiring is used for the ampliiier-dctector LDI, the operation will as follows: Voice currents incoming from the ine will pass into the transmitting path 'llil and enter the delay circuit TD1. ln the meantime the ampliiier-detector Titi) is operated to cause current to flow a the operating Winding o of the relay rllill `which attracts its armature. As soon as ti, e armature leaves the back Contact, ground is removed from the point m, thereby removing the short-circuit :trom the operating 'windings 0 ot the TSS relays and the TEE() relays which are immediately actuated.

luring the time that the armature of the relay Thil is passing to its front contact, current flows from battery through the S90-ohm re `stance to the point m and thence over the hack Contact of the relay TVl-ltll and through the 50G-ohm resistance r and through the locking winding Z of the relay rlllvil, this current flou/img by virtue of the removal of the s mrt-circuit from the resistance r and Wind ing Z when the armature ci the relay TMl actuated. 1llllhen the armature of the relay i lil reaches its iront contact the previously charged condenser c is discharged and the This relay is given a hannover time by virtue ot the fact that a charging current into condenser o flows the BflOO-ohm resistance and il its Winding, thus maintaining the dovfor a oredetermined period ai:

armature or the relay "Eli/l1 leaves its contact. s soon as the armature of theY relay Tllltl] leaves its bach Contact, the circuit into locking Winding Z ot the master relay llv'l., is opened, lent/ing the master relay free to -tall oli in response to cessation of the signal current. Upon arriving at its front llfl contact the armature of the relay TVHO1 connects the condenser c (which had been previously charged positively through the holding windings h of the relays TEHO1 and TEHOAL) to the point m, thereby enabling.

the condenser to discharge to the negative batter-y through the C-ohm and 90-ohm re- .K

the release of the hangover relay TEHOldue to the fact that a charging current flows through the windings 7L ot the TEHO relays to charge the condenser c', this charging current flowing in such a direction as to cause` holding windings h to hold up the. armatures ot the TEHO relays until the charging current through the 27,000-ohm resistance has decayed to a predetermined value. Conseq uently, the TEHO relays do not release their armatures for a predetermined time after We TSS relays release their armatures,- since ein.,

the latter relays release their armaturesinstantlv when the armature of the relayv y sion from the distant terminal is received by4 the .radioreceiver RR and transmitted over TVT-l0, falls off its front contact.

Tn connection with theTSS relays it will be remembered that they were energized through their operating Vwindings as soon as the armature of the master relay TM1 ,lett its back contact to remove the short-circuit from the point m. `The TSS relays upon being energized remove the short-circuits from the paths TL, and `TLl, respectively, thereby completing the transmission circuit through the privacy mechanism PM. The armature ot' the relay TSSl'at its front-'contact connects ground through the small 500- ohm resistances 1" to the bucking windings Z) ot the TSSrelays, thereby increasing the current through these windings (which previously had been very small dueto the 8,000- ohm resistance 1^ in series therewith). Hence an opposing pull is produced upon the armatures of the TSS relays as soon as their armatures have been shifted, such pull being in a direction to o ose the holdin@` torce- This y exerted by the operating windings. I bucking or opposing torce will be less than that exerted by the operating windings but tends to eEect a quick snappy release of the armatures of the TSS relays as soon as cur-r rent ceases to How through the operating windings upon the release of the voice hang* over relay TVI-T01.

Returning, again, tothe TEHO relays which were energizedv in the manner previously described, it will be notedthat in the normal condition of thevcircuit the receiving path is `normally operative from the receiving line HL2, through the path RLl, through the privacy mechanism PM, and through the path RL1 to the path RLl. When the TEHO relays are energized, however, so that their contacts are open, the balanced transf ormers controlled thereby have their wind-r` ings connected in opposing relation, thereby blocking the connection from the line HL2V to thel path RL1V and similarly blocking theV connection from the path RL1 to the path RL1. Consequently, the voice currents which pass through the delay circuit DT1 by the time the TSS relays have operated, are free to pass through the privacy mechanism and over the line TL2 to the radio transmitter TT fromwhich they arey radiated to the distant terminal.

When the voice currents cease the TSS re.

lays fall oil after an interval suicient to alecho currents passing over the transmitting line TL1 come back over the receiving line RL2` to cause false operation of the amplifierdetector RADl. As soon as the TEHO re- A lays release, however, the receiving circuit is innormal receiving condition.

It, under these circumstances, transmis-k y thelines RLS and RL2 in tandem, such voice currents will pass into the path RLl, through the privacy mechanism PML into the circuit RL1, and thence over the circuit RLl tothereceiving delay circuit RDl. Some of the energy passes over the X1 wiring, however, to-the ampliiier-detector RADl, thereby energizing the master relay RM1, which in turn causes the relay REI-T01 to be-energized by removing the short circuit from-its oper-KY ating winding 0. The relay REI-T01 opens the operating circuit of the master relay TM1 and thereby prevents the amplifier-detector TADl from exercising any control over the TSS and TEHO relays previously described. g

The armature of the relay RM1 upon reaching its front contact causes the discharge of the condenser c and completes a circuit through the Yholding winding of the relay REHOI. In the meantime, by the time the relay REHOl has pulled up its arma-ture to disable the transmitting voice-operated apparatus,vthe voice currents have passed through. the delay circuit RDl and pass on to the terminal line L. Y

When the voice currents cease the relay `RM1 releases its'armature,` again short-circuiting the operating winding of the relay REHOl. Said relay does not immediately release, however, as a charging current flows through its hold-over winding L and through IAX VLeonesa former arrangement do not oppose each other and transmission may talre place freely-:trom the circuit RLS to the circuit HL2. When the relay TEHO2 is operated in response to voice currents received over the transmitting 'line TL2, its contact is opened and the transtormer windings oppose eachother so that-transmission does not take placethrough the line EL3 to the line RL2 and consequently overloading currents t will not be transmitted into the line RL2.

Where that portion of the receiving path EL3 extending trom the receiving station to the transmitting station is relatively long, the overloading eiiect may be serious in the line EL3. This may be talren care of by a relay R3 operated over an auxiliary line XL?, from an additional contact ot the relay at the radio transmitter. By use of the wiring Y3 the relay R3 controls the circuit of the relay TET-TQS at the receiving station which, by means of its contact controls a balanced transformer arrangement similar to that controlled by the relay TEHO2 at the radio transmitter whereby transmission from the radio receiver RR to the line RL?, will be prevented when the radio transmitter TT is operated in response to speech. Tt the overloading effect occurs in the `radio receiver RR itself, the relay TFLHOS may have an ad ditional contact whereby the radio antenna AR may be disconnected by using the wiring X3.

Since the auxiliary line XLS involves a certain delay in transmission before the relay B3 will operate while the radio transmission Jfrom the radio transmitter TT to the radio receiver RR is almost instantaneous, lit will of course be necessary to provide in the receiving circuit at the receiving station a delay circuit BB3 to enable the relay TETTO3 to operate before the voice current-s received from the radio transmitter TT atthe receiver BR will have had time to be transmitted to the line EL3. Where the line XLS is fairly long this will represent a considerable disad-A vantage and the amount of delay at RDS' may be considerably reduced by operatingy the relay TETTO3 by means of the radio currents received from the radio transmitter TT. This may be accomplished by changing the relay TETTO3 from its wiring YS to an alternative wiring X3 leading to the output ot an amplifier-detector TADS. This amplilierdetector should be so adjusted that the relay TETTO3 will be non-responsiveto current received from the transmitting station at the distant terminal but will respond to the .much greater current received from the radio transmitter TT. lVhen the overloading etlect is not too large in the receiver RR the input of the amplifier-detector TAS may be connected over the wiring Y3 to the output ot the radio receiver' RR. Consequently, when voice-modulated radio currents are received from the transmitter TT the amplifier-detector Til)3 causes the relay T EHO3 to disable the connection to the receiving line RLS. The operation or" the ampliiier-detector TAD3 from the radio receiver RR requires that the antenna AR- be not disabled by the relay TEHOS and consequently with this method the antenna AT while discriminating against reception from the transmitting antenna at the distant terminal. Tn this case the amplilier-detector TADgis changed to the wiring X2. The current normally received from the distant radio transmitter in the auxiliary radio receiver RR with this arrangement will be very small as comparedr with that received in the receiver RR and since its esponse to the radio transmitter TT is very auch greater, the initial voice wave from zie latter transmitter will have suthcient amplitude to operate the relay TPH-TO3 and only a minimum amount of delay in the delay circuit RDS will be necessary to enable the relay Thil-TO3' to operate before the'voice currents arrive at the switching point.

be omitted entirely without producing bad results. When the amplifier-detector TAD3 operated trom the auxiliary receiver1 RR the antenna AR ot the main receiver RR may be changed to the wiring X.3 in which case any effect of overloading in the radio re eiver will be prevented by the operation oit` the rela.y"TEl-T03.

Tt will be observed that the arrangement so tar des ribed involves main voice-controlled apparatus at the control station and auxiliary voice-operated apparatus at the radio transmitter and radio receiving station. The former is necessary in order to efect the switching operations of the privacy mechanism. The apparatus aty the radio nsmitter is necessary in order to prevent transmission of noise tro-m the radio trauer 'i to the receiving line during re- ,cep on, ile the voice-operated apparatus at the receiving` slat-ionis necessary to prevent k.overloading he receiving channel voice z .nsmission over the transline. `While the voice-operated appa-v the radio transmitter and radio reet'fective for the supmit rat-us ceiver might be made D viding voicecontrolled equipment at the In., tact, the delay circuit RD3 may in such case sion ot singing and echoes without procontrol station, if no privacy mechanism PM were to be taken care of there is an additional reason for providing voice-operated apparatus at the control station even in the latter fase. As has been previously pointed out the delay circuit 'UL may be made very small or may even be omitted, it the ainplierdetector TADZ is made very sensitive and in addition, the voice currents are kept to a standard volume While at the same time the noise received from the line TLZ is kept to a minimum. N ovv the noise arising from the line TL2 itselt may be kept very low ir" the line l 2 is laid in cable but there is the connecting line L to be taken care of, which may iead across a continent to a subscriber, and in many cases this terminal connecting line may be fairly noisy. lt is therefore necessary to provide the voice-operated apparatus at the controlling station in order that the t:ansmitting` path may be maintained normally disabled at that point, thereby preventingv the transmission of noise from the iine L to the ampliier-deteotor TAD2 at the transmitting station.

As has been previously mentioned, it is desirable to keep the delay circuits at theV .'f'adio transmitter and radio receiver small so as to reduce the possible time during which lockout may take place. Vith the arrangement so far described, Where voice-controlled apparatus is provided both at the control station and at the radio transmitting and receiving stations, the lockout time is the time of transmission from the control station at one terminal to the control station at the other. For example, suppose the subscriber at the line L talks and the voice Waves coming from his set operate the ampliier-detector TAD, at the control station, thereby disabling the receiving` path at the control station. lf it should happen that the distant talker commenced talking Within a period of time equal to that required for transmission from the control station of the distant terminal to the control station at the terminal shown, such current received trom the distant terminal will be blocked and cannot get to the subscriber at L, due to the disablement of the receiving path RLP In the meantime the subscriber at L, When his transmission arrives at the distant terminal control station, Will find his transmission has been previously blocked by the distant subscriber. Both subscribers might thus talk for some time Without either subscriber ont? ,caring through to the other.

The above diiiculty arises because each subf' fiber can block the other at the point of the four-wire circuit nearest the terminal. lf the effective blocking action of the two talkers can be transferred to points nearer the ini-oldie of the intervening circuit, the possible l For example,

lockout time Wiil be reducer Y if the blocking eected by the two subscribers took place at points separated by Zero transmission time, the lockout could only take place when both subscribers commenced talking at the same instant. ln accordance with the present invention it is proposed to reduce this lockout time to the time of transmission from one radio transmitting station to the radio transmitting` station at the distant terminal. This time Will include the time of transmission through the ether, which is practically negligible from the standpoint ot lockout, and the time of transmission over the Wire line such as the line RLS from the radio receiver to the radio transmitter, which time may be made very small it the transmitting and receiving' stations are fairly close together at each terminal.

ln order that each subscribers blocking action be made effective against the other suhscriber at the radio station instead of at the terminal station, a voice-controlled' equipment is associated With the receiving line at the radio transmitting station and the point of connection of the voice-controlled equipment associated with the receiving line at the control station is shifted so as to be bridged across the line ahead of the point at which it is disabled by the voice equipment associated with the transmitting line. Accordingly, as shown in the drawing, an amplifier-detector RAD, is bridged across the receiving line RLQ at the transmitting station and controls a relay REHO2. The circuit of the relay TSS2 Will. then be changedv from the direct connection to battery over the X2 Wiringv to the Y2 Wiring Which leads to battery over the contact of the relay REIHL. At the control station the input of the ampliiier-detector RAD, Will be changed from the X', Wiring' to the Y1 wiring; so that it is in effect associated With the line HL2 ahead of the disabling means controlled by the contacts of the relavsTEI-IQ and TEHOQ. A delay circuit RD, is in this case also connected between the bridge point of the Yl Wiring; and the disablingmeans controlled by the contact of the relay TEHOl.

Suppose novv the subscriber talks over the line L and operates the amplifier-detector Tell, thereby under the control oi the TSS relays opening` the transmitting path through to the line TL2 and at thel same time causing the TEHO relays to disable the connection from the receiving line RLrz through the privacy mechanism PM to the receivinoj path RL. It Will be observed that now the receiving path is disabled but the amplifierdetec-tor arran ,freinent RAD, is not disabled as it is associated with the line RLZ ahead ot the disabling means controlled by the TEE() relays. W hen the voicecurrents arrive at the transmitting station the ampliiier-detector TAD2 Will be operated and through the relay Thil-IO., will disable the connection from the line EL3 to the lineRL2 at the transmitting station. The distant talker is now effectively blocked at this point. If, however, voice current from the distant talker had arrived over the line EL3 so as to enter the amplitier-detector RADZ before the relay TEHO2 operated, the relay REHO2, in re sponding would disable the relay TSS2 and thereby prevent the relay TEHO2 from operating. Thus the receiving path would still be open to the control station. The current arriving at the control station from over the line RL2 would enter through the wiring Y1 into the amplifier-detector RADl (the path through the Y1 wiring 'not being blocked by the action of the TEHO relays), thereby causing the relay REHOl to open the circuit of the master relay TM1 of the voice-operated equipment associated with the transmitting path at the control station. The delay circuit RDl now functions to holdup the transmission of the voice current from the line RL2 to the privacy mechanism PM until the disabling of the master relay TM1 has had time to effect the restoring of the TEHO relays. As soon as this latter event occurs, the voice current from the delay circuit passes l through the privacy mechanism PM and thence over the circuit RLl to the subscribers line. .Thus it will be seen that 4although the subscriber talking over the line L had operated the voice equipment at the controlstation and had set the circuit into transmitting condition up to thetransmitting station, if the distant talkers current should arrive at t-be transmitting station before the voice currents from the line L arrived thereat the talker associated with the line L would fail to lockout the distant talker and the apparatus at the control station would be restored to receiving condition so that the distant talker would have control of the circuit.

Where it is desired to restore the TEHO relays more quickly the connection of these relays may be changed' from the XQ wiring to the Y1 wiring. Then relay REI-101 will restore relays TEHOl and TBI-IO1 through its eXtreme left hand contact without producing the result indirectly through the relay TMl, thus reducing thetime required for the operation.

A little consideration will show that if the current from the distant talker arrived lat his transmitting station, prior to the arrival of the current from the line L at the transmitting station shown, by any time interval less than that required for a wave to be transmitted from the distant transmitter to the receiver RR and thence over the circuit EL3 to the transmitting station, both talkers will disable their respective receiving paths and lock each otherY out. If, on the other hand, the talk from one subscriber arrives at his transmitter ahead of the time that the talk from the other subscriber arrives at the other transmitter by a time interval greater than the time of transmission from transmitter t0 transmitter, the first subscriber to talk will obtain control of the circuit without any possibility of the other being able to lock him out. Y

It is, of course, desirable tomaintain the transmission loss of the transmitting path TL2 substantially constantpfrom the control otlice to the radio transmitter since a change in loss may cause a poor signal-to-noise ratio or overloading in the transmitter TT even though the relay operation is not impaired due to 'the high relay sensitivity. In order to enable an attendant at the transmitting station to make occasional adjustments at times When the circuit is not actually being used for transmission, arrangements may be made to transmit pilot waves over the line TL2 from the control station, the attendant by suitable means observing any change in the amplitude of the received pilot wave and then making adjustments to bring the amplitude to normal. F or this purpose oscillators O and O may be provided at the control station and the connection of the line TL2 changed to the Y1 wiring instead of the X1 wiring to bring the oscillators into circuit. The waves of frequencies f1 and f2 from the two oscillators will then be transmitted over the line TL2 at all times when the relay TSS1 is not operated. When voice currents are applied to the transmitting circuit so that said relay is operated it short circuits the oscillators O and O and prevents the transmission of the pilot waves at the transmitting station. The amplitude of the pilot waves may be observed by means of a volume indicator TVL, and if the volume is below or above normal the volume control apparatus TVGZ may beadjusted by the attendant at the transmitting station.

With this arrangement a slightly different circuit for operating the relay TSS2 is provided. yInstead of having the amplifier detector TAD2 bridged across the line by means of the X2 wiring, the line bridge is changed to the Y2 wiring so thatthe wave of frequency f1 from the oscillatorl O will be selected by means of a filter F1 into an ampliier-detector TAD2 and the wave of frequency f2 from the other oscillator will be selected by means of the filter F2 into the amplifier-detector TAD2. During non-talking intervals the two pilot waves will, while opera-ting these two amplifier-detectors, keep the-relays RQ and RVZ energized, thereby maintaining the relay R2 energized. vThe connection of the relayA TSS? is shifted from the X2 wiring to the Y2 wiring so that the circuit of the latter relay is now controlled by the relay R2. Consequently, as long as the waves of frequencies f1 and f2 are present the circuit of therelay TSS2 is opened and the transmitter TT maintained short circuited. When vvoice currents are applied` to the circuit and both soV Waves f1 and suppressed in the manner previously described, the relay R2 is deeiiergized by the falling oii' of the relays Rg and R2 and the relay TSSZ is energized over the back Contact of the relay B2 to remove the short-circuit from the radio transmitter.

V `With the foregoing arrangement the function of the delay circuit TD2 is not primarily to delay the transmission of voice currents but to hold up the transmission of the pilot Waves (which enter the delay circuit as soon as. the voice current ceases) iintil'tlie relay T552 has had time to release in response to the pilot Waves. More than one pilot Wave i is provided in order to prevent false operation when the circuit is in condition for voice transmission. lVlien the relay TSSB has been operated to put the transmitting circuit into transmitting condition, the short-circuit across the transmitter TT will not be again closed unless both relays R-2 and RZ are energized. While it might happen that the voice current would contain a Vfrequency cor responding to one oic the filters F1 and F2, it Would rarely happen that the voice current would contain both frequencies. @ne Wave alone Would not cause false operation of the relay T352 and blocking ot the voice current.

It Will be obvious that the general principles herein disclosed may be embodied in many other organizations Widely ldilierent :from those illustrated without departing 'from the spirit of the invention as defined in the following claims.

lVhat is claimed is:

1. In a radio telephone system, a control station at Which connections may be made to a terminal line,.a radio transmitting station, a radio receiving station, a transmitting line extending trom said control station to said radio transmitting station, a receiving line extending Jfrom said radio receiving station to said control station, voice-operated means at the control station and responsive to voice currents transmitted vover said transmitting line for disabling the receiving line at said control station, voiceoperated means at said control station and responsive to voice currents received over said receiving line for preventing transmission over said transmitting line from the control station, Vmeans at said radio transmitting station normally preventing the radiation of signaling currents transmitted over said transmitting line, signal-operated means at. said radio transmitting station responsive when voice currents are transmitted over said transmitting line to render said radiation-preventing means ineffective, and means at said radio receiving station responsive to radio transmission from said radio transmitting station to prevent transmission over said receiving line from said radio receiving station.

2. In a radio telephone system, a control receiving line at said control station, voiceoperated means at said control station and responsive to voice currents received over said receiving line for preventing transmission over said transmitting line from the control station, means at said radio transmitting station normally preventing the radiation ot signaling currents transmitted over said transmitting line, signal-operated means at said radio transmitting station responsive WhenV voice currents are transmitted over said transmitting line to render said radiatioii-preventing means ineimiective, a radio receiver at said radio receiving station Jfor receiving signals from the distant terminal and transmitting them to said radio receiving line, and an auxiliary radio receiver at said radio receiving station responsive to radiation of signals from said radio transmitting station to prevent the transmission of signals from said first-mentioned radio receiver to said receiving line.

3. InA a radio telephone system, a control station, at Which connections may be made to a terminal line, a radio transmitting staf tion, awradio receiving station, a transmitting line extending from said control station to said radio transmitting station, a receiving line extending from said radio receiving station to said control station, voiceoperated means at the control station and responsive to voice currents transmitted over said transmitting line for disabling the receiving line at said control station, voiceoperated means at said control station and responsive to voice currents received over said receiving line for preventing transmission over said transmitting line from the control station, means at said radio transmitting station normally preventing the radiation of signaling currents transmitted over said transmitting line, signal-operated means at said radio transmitting station responsive when voice currents are transmitted over said ,A

transmitting line to render said radiationpreventing means ineii'ective and to disable said radio receiving line at a point in the neighborhood of said transmitting station,

and means at said receiving station responf sive 4to transmission of signals from said radio transmitting station to prevent the transmission of received signals from said radio receiving station to said receiving line.

In a radio telephone system, a control 7,30

station at which connections may be vmade to a terminal line,a radio transmitting station, a radio receivingstation, a one-Way transmitting path extending from said control station to said radio transmitting station, a one-Way receiving path extending from said radio receiving station to said conw trol station, said patas being 'so isolated from each other that no part of either path serves as a common two-Way transmission medium for both paths but the path to one ot said radio stations passing in the immediate vicinity of the other radio station, voice-operated means at the control station and responsive to voice currents transmitted over said transmitting path for disabling the receiving line at said control station, voice-operated means at said control station and responsive to voice currents received over said receiving path for preventing transmission over said transmitting path from the control station, ieans at said radio transmitting station normally preventing the radiation of signaling currents transmitted over said transmitting path, signal-operated means at said radio transmitting station responsive when voice currents are transmitted over said transmitting path to render said radiation-preventing means ineiective, means responsive when voice currents are effectively transmitted from said transmitting path to said radio transmitting station to disable said receiving path at one oiE said radio stations, and means associated with said receiving path in the vicinity of said transmitting` station and responsive to signals received over said receiving path from the distant terminal to prevent radiation from said radio transmitting station in response to currents tra-nsmitted over said transmitting path, said voice-operated means associated With the i'e ceiving path at the control station being so arranged as to defeat the disabling ot said receiving path at the control station under the control ot the voiceoperated means associated With the transmitting path at the control station When said voice-operated means associated With the receiving path in the neighborhood of the radio transmitting` station has been effectively operated.

5. In a radio telephone system, a control station at Which connections may be made to a terminal line, a radio transmitting station, a radio receiving station, a one-Way transmitting path extending trom said control station to said radio transmitting station, a oneivay receiving path extending from said radio receiving station to said control station7 said paths being so isolated from each other that no part of either path serves as a common two-Way transmission medium for both paths but the path to one of said radio stations passing in the immediate vicinity of the other radio station, voice-operated means at the control station and vresponsive to voice curf' rents transmitted over said transmitting path .means at said radio transmitting station normally preventing theradiation of signaling currents transmitted over said transmitting path, signal-operatednieans at said radio transmitting station responsive when voice currentsv are transmitted over said transmitting path to rendersaid 4radiation-preventing means ineffective, meansresponsive when voice currents are eit'ectively transmitted from said transmitting path to said radio transmitting station to disable said receiving path at one of said radio stations, andy means .associated Withsaid receivingpath in the vicinity of said transmitting station and responsive to signalsreceived over said receiving pathl from thedistant terminal to pre- Yvent radiation from saidl radio transmitting station in response to currents transmitted vover said transmitting path.

In a radio telephone system, a control station at which connections may be made to a terminal line, a radio transmitting station, a radio receiving station, `a transmitting line extending from said controlstationfto said radio transmittingstation, areceiving line extending from said radio receiving stavtion to said control station, means or normally disabling said transmitting line atthe control station, voice-operated means associated with said transmitting line at the control station for defeating said disabling E means, voice-operated means associated with said receiving line at the control station for disabling said transmitting line, means at said control station for maintaining the-volume of the voice currents applied to said transmitting line ata substantially constant volume, highly sensitive voice-operated means associated with said transmitting line at said' radio transmitting station, said last mentioned voice-operated means `being effectively responsive to the Weak initial part ot a voice current Wave, and means operated by said voice-operated means at the radio transmitting station to normally prevent transmission from said transmission station except when said voice-operated means is effectively operated, and means controlledv by said voice-operated. means at said radio transmitting stationto disable said receiving line ata point remotefrom said control station.

7. In a radio telephone system, a control station at which connections may be made to a terminal line, al radio transmitting station, a radio receiving station, a transmitting line extending from said control station to said radio transmitting station, a receiving line extending 'from said radio receiving station to said control station, voice-operated means associated With said transmitting line at said control station for normally controlling the transmission ot pilot Waves over said transmitting line to the radio transmitting station, an adjustable transmission element at said radio transmitting station for making transmission adjustments in accordance with the pilot Waves received thereat, said voice-operated means at the control station operating in response to voice currents to prevent the transmission of said pilot frequencies and to permit the transmission of voice currents over said transmitting circuit, switching means at said radio transmitting station operating when said pilot Waves are received to prevent radiation from said radio transmitting station but to permit radiation oil' energy corresponding to voice currents received over said transmitting line when the pilot Waves cease.

8. In a radio telephone system, a control station at which connections may be made to a terminal line, a radio transmitting stat-ion, a radio receiving station, a transmitting line extending from said control station to said radio transmitting station, a receiving line extending from said radio receiving station to said cont-rol station, voice-operated means associated with said transmitting line at said control station for normally controlling the transmission of pilot means over said transmitting line to the radio transmitting station, an adjustable transmission element at said radio transmitting station for making transmission adjustments in accordance with the pilot Waves received thereat, said. voice-operated means at the control station operating in response to voice currents to prevent the transmission of said pilot waves and to permit the transmission of voice currents over said transmitting circuit, switching means at said radio transmitting station operating when said pilot Waves are received to prevent radiation from said radio transmitting station but to permit radiation ot energy corresponding to voice-currents re ceived over said transmitting line when the pilot Waves cease, and means controlled by said switching means at the radio transmit ting station for disabling said receiving line at a point remote from said control station when said pilot Waves cease.

9. A transmission system including an intermediate section With connecting sections, means at each end of said intermediate secv tion to block the transmission of Waves in either direction While Waves are passing in the opposite direction, means at points of the teinber, 1929.

EDMUND R. TAYLR. SUMNER B. WRIGHT.. 

